The electrophotographic method comprises a charging stage in which a uniform electrostatic charge is conferred on a photosensitive body employing a photoconductive material, an imaging stage in which there is irradiation of light and the formation of an electrostatic latent image, a developing stage in which toner is electrostatically affixed to the area of the latent image, a transfer stage for transferral to a toner image support, a fixing stage in which said toner image is fixed to the toner image support by pressure, heat or flash of light, etc., a cleaning stage in which untransferred toner remaining on the photosensitive body is removed and a discharging stage in which the electrostatic charge on the photosensitive body is eliminated and it is returned to its initial state, and prints are obtained by repetition of these stages.
Cold pressure fixing, which is one of the fixing methods used in an electrophotographic printer, has the advantages that immediate operation is possible, power consumption is low since it does not use a heater as a heat source and there is no danger of burning in the fixing region, but it has disadvantages such as the print fixing properties being inferior and a conspicuous print lustre and low quality, so in general the use of heat fixing systems is more advantageous. As such heat fixing systems, there are known contact heat fixing systems based on hot roll fixing and non-contact heat fixing systems based on fixing by a flash of light or oven fixing by passage through the heated atmosphere of an electric heater.
The present invention relates to fixing by means of a light flash which is a typical non-contact heat fixing system, and the flash fixing system is a method in which the toner visible image is exposed to the emission spectrum of, for example, a xenon lamp or halogen lamp for a short time of no more than milliseconds, so that the toner is softened and fused by the radiant heat thereof and fixed to the toner support (Japanese Unexamined Patent Publication No. 7-107805), and it has the following advantages.
(1) Since it is non-contact fixing, there is no deterioration in the print resolution at the time of development.
(2) There is no waiting time after switching on the power source and a `quick start` is possible.
(3) Even where recording paper or the like is jammed inside the fixer due to system failure, burning does not occur.
(4) Good fixing properties are shown irrespective of the type of toner support (quality of the recording paper, tack paper, thick paper, etc.)
(5) Since only the toner, which comprises areas of black, is heated, there is little heat shrinkage of the recording paper or the like, the paper feeding properties are excellent and high speed printing is possible.
However, since the flash fixing system comprises non-contact heat fixing, the level of energy dissipation to the surroundings is high and, because it is flash light energy, the thermal efficiency is poor compared to hot roll fixing. In other words, it is fixing system with a high power consumption. Furthermore, with the flash fixing system there has been the problem of decomposed materials, in that the surface temperature of the toner composition instantly reaches a high temperature of several hundred degrees due to the irradiation of a sudden high energy flash of light in an extremely short time, and some of the additives in the toner composition are decomposed and gasify, releasing an unpleasant smell or generating toxic gases.
Generally speaking, with a flash fixing system printer, in order to remove the decomposed materials at the time of the flash fixing, in the flash fixing region there is adopted a method whereby these decomposition products are drawn in, passed through a filter of active carbon or the like, and the toxic gases adsorbed and collected. However, there has been the problem of increased running costs since a filter is used and since the replacement life of this filter is shortened.
The present invention has been made to resolve the aforesaid problems, and it provides a toner composition for electrostatic latent image development where, by suppressing the generation of decomposition products in a printer employing a flash fixing system, a filter is made unnecessary or the problem of increased running costs because of the shortening of the filter replacement life is resolved.